Unit24CompassandGyro-compass..doc

Unit24 Compass and Gyro-compass 罗经和陀螺罗经 I The Magnetic Compassed Magnetism磁罗经和磁场 The principle of the present day magnetic compass is no different from that of the compasses used by ancient mariners. It consists of a magnetized needle, or an array of needles, allowed to rotate in the horizontal plane. The superiority of the present day compasses over ancient ones results from a better knowledge of the laws of magnetism which govern the behavior of the compass and from greater precision in construction.现代罗经使用的原则与过去海员所使用罗经的原则，没有什么不同。它包括一根磁针或者一列磁针，在水平面内旋转，现代罗经比古代罗经优越是由于对控制罗经的行为相关的磁学的规律有了更好的了解，还由于罗经制造时有了更好的精确度。 Any piece of metal on becoming magnetized will develop regions of concentrated magnetism called. Any such magnet will have at least two poles of opposite polarity. Magnetic force (flux) lines connect one pole of such a magnet with the other pole. The number of such lines per unit area represents the intensity of the magnetic field in that area. If two such magnetic bars or magnets are placed close to each other, the like poles will repel each other and the unlike poles will attract each other. 任意一根金属被磁化，是磁学发展的集中领域。任意这样的磁体都会至少有磁性相反的两极。磁感线将这种磁体的一极与另一极连接起来。单位区域内磁感线的密集程度可以表现出该区域磁场的强度。如果两条这样的磁铁或磁性物质被放置的很近，相同的极将互相排斥，不同的极将互相吸引。 Magnetism can be either permanent or induced. A bar having permanent magnetism will retain its magnetism when it is removed from the magnetizing field. A bar having induced magnetism will lose its magnetism when removed from the magnetizing field. Whether or not a bar will retain its magnetism on removal from the magnetizing field will depend on the strength of that field, the degree of hardness of the iron (Retentively), and also upon the amount of physical stress applied to the bar while in the magnetizing field. The harder the iron, the more permanent will be the magnetism acquired. 磁性可以是永久性的，或者感应的。一根具有永久性磁性的磁铁当它从磁场中移出的时候将保持其磁性。一根具有